The new cultivar is the product of chance discovery. The new variety originated as a naturally occurring branch mutation of the unpatented ‘Mamasun’ variety of Mandevilla sanderi. 
The new variety was discovered by the inventors, Martijn Los and Maurits van der Arend, both citizens of the Netherlands, on Dec. 1, 2009 in a commercial greenhouse belonging to the inventors in Klazienaveen, The Netherlands. After identifying the new variety as a potentially interesting selection, the inventors continued confidential testing and propagation of ‘Patmandewi’ assessing stability of the unique characteristics of this variety.
Asexual reproduction of the new cultivar ‘Patmandewi’ was first performed at the commercial greenhouse belonging to the inventors in Klazienaveen, The Netherlands by vegetative cuttings in early 2010. Access to all plants was restricted, as plants were kept in a greenhouse not open to the public. Through subsequent propagation by vegetative cuttings, multiple generations have been reproduced, which have shown that the unique features of this cultivar are stable and reproduced true to type.